Technical-economical model for the prevention of "babesiosis" and "anaplasmosis" in bovines

Source: INTA

The babesiosis (Babesia bovis, Babesia bigemina) and the anaplasmosis (Anaplasma Marginale) they are illnesses in bovines that are usually included under the generic name of "sadness". Its occurrence depends on the presence of the common tick in bovines, the Boophilus microplus, only transmitter of those babesias and it participates occasionally in the dispersion of the A.marginale as well.

Most bovines are naturally resistant to suffer these illnesses when the primary infection takes place during the first seven months of age, which confers immunity for life. Passed that period the natural resistance falls and the graveness of the primary infection is directly related to the animal’s age.

These illnesses are known from the beginnings of commercial cattle raising in the north of Argentina for the devastating effect in animals introduced from areas that are free of ticks. However, they also affect animals born and raise in areas infested with the command ticks.

Relationship with the ticks

The probabilities of occurrence of anaplasmosis or babesiosis are directly related to the proportion of calves that were not naturally infected until the seven months of age. This depends on the quantity of infected ticks in the establishment. The population of this parasite is conditioned by environmental factors, the frequency of insecticides use and the exploitation of Indian races which are resistant to the ticks. In turn, the load of B.microplus can vary between years; therefore, the situation of the calves will vary in its rate of natural immunity because of this.

The INTA uses a system developed in Australia to determine the risk of occurrence of babesiosis and anaplasmosis in bovines born in areas infested with the B.microplus tick and it produces a vaccine to protect them from these illnesses.

It is described next how these techniques can be applied using simple parameters to determine if the investment in that protection system can be economically justified.

Technique to prevent babesiosis and anaplasmosis in bovines

You can predict the occurrence of babesiosis and anaplasmosis by determining the proportion of calves that present specific antibodies by the 7-9 months of age.

INTA developed a live vaccine combined against babesiosis and anaplasmosis. The same one contains "A.centrale", kindred species to "A.marginale" but of less pathogen power that confers partial protection against the effects of it. It also contains attenuated stumps of B. bovis and B. bigemina. This vaccine was developed for its use in cattle raising for the Argentinean north and exclusive application in bovine younger than 10 months of age. A single dose induces immunity against babesiosis and anaplasmosis for the entire useful life of the animals. Their application is recommended in cases in which an important proportion of calves is not immunized naturally.

Sample taking and results interpretation

Blood from the animal (around 7 months of age) should be obtained for the analysis of antibodies. The number of bovine to bleed will be:

The hole group, when is not more than 20 calves.

20 samples, when the group is from 21 to 100 calves.

21-100 samples (20%), when the group is from 101 to 500 calves.

100 samples, when the group is bigger than 500 calves.

It is considered that risk of occurrence of babesiosis and anaplasmosis exists when the percentage of positive reactors is inferior to 75% of the analyzed total. Although one can argue that this value could even be incremented to reduce the hypothetical rate of susceptible bovines, it is worth to point out that not all the primary infections produce the illness and not all negatives will be infected.

Economic analysis

Two hypothetical groups of reinstatement females will be analyzed, one relatively small of 100 animals and a bigger one, of 1000 animals. Animals not vaccinated against babesiosis and anaplasmosis were also considered.

According to what was indicated, in the group of 100 animals, we would observe 7 sick animals and 3 dead ones and in the group of 1000, 70 and 30 respectively. It was considered that the average live weight was of 220 kg and the price for live kg was considered to be $0,80, therefore each dead animal was valorized in $176.

A therapeutic treatment for a single sick animal (3,5 mg of diminazene and 20 mg of oxytetracycline per each kilo of live weight) with a cost of $7 was considered.

The animals that recovered from the infection were affected in their growth, delaying in one year their date of service.

Applying a conservative approach, it was considered that the professional costs, of manpower and of communications, for the attention of the illness were identical to those of the vaccination, therefore they were not included in the analysis of economical losses nor were they included in the corresponding analysis of prevention expenses.

Hypothetical cost of the prevention

It was considered the analysis of antibodies in 20 animals for the group of 100 veal and of 100 for that of 1000 veal, with a cost of $3,50 per analysis.

The cost per dose of vaccine was considered to be $2,10 for the group of 100 and $1,68 for that of 1000 (considering a 20% discount for high quantity of doses according to the effective tariffs mentioned above).

Benefits/costs relationship

It was observed that the vaccine reduced the losses for these illnesses in 95%. Theoretically, that reduction represents a value of $5,8 (6,1×95%) for each bovine in both the 100 and the 1000 groups, taking into consideration that the cost for each bovine in the hypothetical situation caused a loss of $6,1.

The analysis of this hypothetical case is a tool used to explain the benefits of the technique of prevention. For its rational application there should be considered different death rates in conjunction with different prices for standing livestock. This is important so that cattlemen can relate their experience with babesiosis and previous anaplasmosis in relation to the potential prices of their livestock to decide if it is convenient or not to look for professional attendance for the prevention of the problem.

The price of the livestock is the most important parameter and the proposed system is more efficient when the number of bovines involved is bigger. With superior potential mortalities to 1%, the index benefit-cost for the group of 1000 veal is superior at 1 if the price of the livestock is of $0,80 the alive kg; while a superior mortality to 2% with prices of the alive kg of $0,80 the useful restitution in groups of 100 veal.